The present invention relates generally to a system which can be used when an interventional procedure is being performed in a stenosed or occluded region of a blood vessel to capture any embolic material that may be created and released into the bloodstream during the procedure. The system of the present invention is particularly useful when performing balloon angioplasty, stenting procedures, laser angioplasty or atherectomy in critical vessels, such as the carotid arteries, where the release of embolic debris into the bloodstream can occlude the flow of oxygenated blood to the brain or other vital organs which can cause devastating consequences to the patient.
A variety of non-surgical interventional procedures have been developed over the years for opening stenosed or occluded blood vessels in a patient caused by the build up of plaque or other substances on the walls of the blood vessel. Such procedures usually involve the percutaneous introduction of the interventional device into the lumen of the artery, usually through a catheter. One widely known and medically accepted procedure is balloon angioplasty in which an inflatable balloon is introduced within the stenosed region of the blood vessel to dilate the occluded vessel. The balloon catheter is initially inserted into the patient""s arterial system and is advanced and manipulated into the area of stenosis in the artery. The balloon is inflated to compress the plaque and press the vessel wall radially outward to increase the diameter of the blood vessel.
Another procedure is laser angioplasty which utilizes a laser to ablate the stenosis by super heating and vaporizing the deposited plaque. Atherectomy is yet another method of treating a stenosed blood vessel in which a cutting blade is rotated to shave the deposited plaque from the arterial wall. A vacuum catheter may be used to capture the shaved plaque or thrombus from the blood stream during this procedure.
In another widely practiced procedure, the stenosis can be treated by placing a device known as a stent into the stenosed region to hold open and sometimes expand the segment or blood vessel or other arterial lumen. Stents are particularly useful in the treatment of repair of blood vessels after a stenosis has been compressed by percutaneous transluminal coronary angioplasty (PTCA), percutaneous transluminal angioplasty (PTA) or removal by atherectomy or other means. Stents are usually delivered in a compressed condition to the target site, and then are deployed at the target location into an expanded condition to support the vessel and help maintain it in an open position.
Prior art stents typically fall into two general categories of construction. The first type of stent is expandable upon application of a controlled force, often through the inflation of the balloon portion of a dilatation catheter which, upon inflation of the balloon or other expansion means, expands the compressed stent to a larger diameter to be left in place within the artery at the target site. The second type of stent is a self-expanding stent formed from, for example, shape memory metals or super-elastic nickel-titanum (NiTi) alloys, which will automatically expand from a compressed state when the stent is advanced out of the distal end of the delivery catheter into the body lumen. Such stents manufactured from self-expandable materials allow for phase transformations of the material to occur, contributing to the expansion and contraction of the stent.
The above non-surgical interventional procedures, when successful, avoid the necessity of major surgical operations. However, there is one common problem associated with all of these non-surgical procedures, namely, the potential release of embolic debris into the bloodstream which can occlude distal vasculature and cause significant health problems to the patient. For example, during deployment of a stent, it is possible that the metal struts of the stent can cut into the stenosis and shear off pieces of plaque which become embolic debris that can travel downstream and lodge somewhere in the patient""s vascular system. Pieces of plaque material can sometimes dislodge from the stenosis during a balloon angioplasty procedure and become released into the bloodstream. Additionally, while complete vaporization of plaque is the intended goal during a laser angioplasty procedure, quite often particles are not fully vaporized and enter the bloodstream. Likewise, emboli may enter the bloodstream as well.
When any of the above-described procedures are performed in the carotid arteries, the release of emboli into the circulatory system can be extremely dangerous to the patient. Debris that is carried by the bloodstream to distal vessels of the brain can cause these cerebral vessels to occlude, resulting in a stroke, and in some cases, death. Therefore, although carotid percutaneous transluminal angioplasty has been performed in the past, the number of procedures performed has been limited due to the justifiable fear of causing an embolic stroke should embolic debris enter the bloodstream and block vital downstream blood passages.
Medical devices have been developed to attempt to deal with the problem created when debris or fragments enter the circulatory system following treatment utilizing any one of the above-identified procedures. One approach which has been attempted is the cutting of any debris into minute sizes which pose little chance of becoming occluded in major vessels within the patient""s vasculature. However, it is often difficult to control the size of the fragments which are formed, and the potential risk of vessel occlusion still exists, making such procedures in the carotid arteries a high-risk proposition.
Other techniques which have been developed to address the problem of removing embolic debris include the use of catheters with a vacuum source which provides temporary suction to remove embolic debris from the bloodstream. However, as mentioned above, there have been complications with such systems since the vacuum catheter may not always remove all of the embolic material from the bloodstream, and a powerful suction could cause problems to the patient""s vasculature.
Further techniques which have had some limited success include the placement of a filter or trap downstream from the treatment site to capture embolic debris before it reaches the smaller blood vessels downstream. However, there have been problems associated with filtering systems, particularly during the expansion and collapsing of the filter within the body vessel. If the filtering device does not have a suitable mechanism for closing the filter, there is a possibility that trapped embolic debris can backflow through the open end of the filter and enter the bloodstream as the filtering system is being collapsed for removal from the patient. In such a case, the act of collapsing the filter device may actually squeeze trapped embolic material through the opening of the filter. The need for existing filters to be deployed in the full flow stream of the vessel without alternative paths for embolus free blood to supply the brain may result in deformation or incomplete deployment of the filter. In other instances, the rate of blood percolating through the filtering material may be slower than the normal blood flow which can either result in inadequate blood flow or promote clogging of the filter. If a filter should become clogged when in use in the carotid arteries, blood flow could be diminished to the vessels leading to the brain. While the brain may be capable of functioning for a very short period of time without sufficient blood flow, blood stoppage of more than thirty to forty seconds could cause the patient to experience a seizure or transient ischemic attacks. If the physician administering the procedure is unaware that the filtering device is clogged and that there is little or no blood flowing to the brain, the injury to the patient can be as devastating as if an emboli itself had caused blockage of the cerebral arteries.
What has been needed is a reliable system and method for treating stenosis in blood vessels which prevent the risk of releasing embolic debris into the bloodstream that can cause blockage in vessels at downstream locations. The system and method should be capable of filtering any embolic debris which may be released into the bloodstream during the treatment, and yet allow a sufficient amount of oxygenated blood to flow past the filtering device to supply vital organs downstream from the treatment site. The system and method should be relatively easy for a physician to use and should provide a failsafe filtering system which removes all embolic debris from the bloodstream. Moreover, such a system should be relatively easy to deploy and remove from the patient""s vasculature. The inventions disclosed herein satisfy all of these needs.
The present invention provides a system and method for capturing embolic debris in a blood vessel which may be created during the performance of a therapeutic interventional procedure, such as a balloon angioplasty or stenting procedure, in order to prevent the embolic debris from lodging and blocking blood vessels downstream from the interventional site. The present invention is particularly useful while performing an interventional procedure in vital arteries, such as the carotid arteries, in which critical downstream blood vessels can become blocked with embolic debris, including the main blood vessels leading to the brain or other vital organs. As a result, the present invention provides the physician with a higher degree of confidence that any and all embolic debris is being collected and removed from the blood vessel when performing high-risk interventional procedures.
The present invention occludes the blood vessel at a location distal to or at the area of treatment in the interventional procedure site, perfuses the blood to enable blood to flow past the occlusion, and filters the blood to capture any embolic debris which may be created during the interventional procedure.
In the present invention, the system includes a filter including filtering elements to occlude a blood vessel and to capture and retain embolic material. The emboli-capturing system of the present invention directs the blood flow through the area where the interventional procedure is to be performed and through the filtering elements located distal to the interventional site, which are designed to capture any friable plaque deposits. Additionally, the present invention allows blood to flow past the filtering elements to provide a continuous stream of blood to the organs located downstream.
In an embodiment of the present invention, the embolic protection system includes a shaft which has a proximal and distal end, and which is adapted to extend distal to the interventional procedure site. A filter including filtering elements is adapted to be located in the distal end portion of the shaft. The filtering elements are adapted to be expandable, and can be deployed within the blood vessel to prevent blood flow past the expandable member, for occluding the blood vessel at a location distal to the interventional procedure site. The expandable filtering elements are further adapted to enable blood to flow therethrough. As a result, even though the expandable filtering elements occlude the blood vessel, the blood will continue to flow past the expandable filtering elements. The blood flowing into and through the filtering elements distal of the interventional site enables the filtering elements to capture embolic material which may be released into the blood in the blood vessel during the interventional procedure. The system further includes a sheath for enabling the filtering elements to expand and contract upon movement of the sheath proximally and distally relative to the filtering elements. The sheath may be located proximal or distal of the filtering elements. The filtering elements are further adapted to be collapsible upon movement of the sheath relative to the filtering elements to retain embolic material captured therein.
The sheath and the shaft of the emboli-capturing system, once deployed within the patient""s vasculature, can be used as a guidewire to allow interventional instruments to be moved along the sheath and the shaft into the area of treatment in an over-the-wire arrangement. This eliminates the need to maintain a separate guidewire in the patient once the sheath and the shaft are in place.
In one particular embodiment of the embolic protection system of the present invention, the filtering elements include a plurality of bristles extending from a distal section of the shaft, and a net located distal of the bristles. The sheath may be movable distally to enable the net and the bristles to expand, and proximally to collapse the net and the bristles to retain captured embolic material. In another particular embodiment, the filtering elements comprise a basket, and the sheath is movable distally to enable the basket to expand, and proximally to collapse the basket. In a further embodiment of the invention, the filtering elements comprise a net in a distal section of the shaft, and a serf-expanding stent located proximal of the net. The sheath is movable proximally to release the net and the stent, and is movable distally to contract the net to retain the embolic material captured therein.
Other features and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments of the invention, when taken in conjunction with the accompanying exemplary drawings.